1. Field of the Invention
The present invention relates to ophthalmic lenses, and more particularly to contact lenses incorporating a compliance indicator comprising a material that when exposed to visible light causes the material to change from transparent to visible over a predetermined period of time, thereby functioning as an alert to the user to replace the contact lenses.
2. Discussion of the Related Art
Myopia or nearsightedness is an optical or refractive defect of the eye wherein rays of light from an image focus to a point before they reach the retina. Myopia generally occurs because the eyeball or globe is too long or the cornea is too steep. A minus or negative powered spherical lens may be utilized to correct myopia. Hyperopia or farsightedness is an optical or refractive defect of the eye wherein rays of light from an image focus to a point after they reach or behind the retina. Hyperopia generally occurs because the eyeball or globe is too short or the cornea is too flat. A plus or positive powered spherical lens may be utilized to correct hyperopia. Astigmatism is an optical or refractive defect in which an individual's vision is blurred due to the inability of the eye to focus a point object into a focused image on the retina. Astigmatism is caused by an abnormal curvature of the cornea. A perfect cornea is spherical whereas in an individual with astigmatism, the cornea is not spherical. In other words, the cornea is actually more curved or steeper in one direction than another, thereby causing an image to be stretched out rather than focused to a point. A cylindrical lens rather than a spherical lens may be utilized to resolve astigmatism.
Contact lenses may be utilized to correct myopia, hyperopia, astigmatism as well as other visual acuity defects. Contact lenses may also be utilized to enhance the natural appearance of the wearer's eyes. Contact lenses or contacts are simply lenses placed on the eye. Contact lenses are considered medical devices and may be worn to correct vision and/or for cosmetic or other therapeutic reasons. Contact lenses have been utilized commercially to improve vision since the 1950s. Early contact lenses were made or fabricated from hard materials, were relatively expensive and fragile. In addition, these early contact lenses were fabricated from materials that did not allow sufficient oxygen transmission through the contact lens to the conjunctiva and cornea which potentially could cause a number of adverse clinical effects. Although these contact lenses are still utilized, they are not suitable for all patients due to their poor initial comfort. Later developments in the field gave rise to soft contact lenses, based upon hydrogels, which are extremely popular and widely utilized today. Specifically, silicone hydrogel contact lenses that are available today combine the benefit of silicone, which has extremely high oxygen permeability, with the proven comfort and clinical performance of hydrogels. Essentially, these silicone hydrogel based contact lenses have higher oxygen permeabilities and are generally more comfortable to wear than the contact lenses made of the earlier hard materials.
Contact lenses may be broadly categorized as daily disposable contact lenses, frequent replacement contact lenses and traditional contact lenses. Daily disposable contact lenses, as the name implies, are worn for a single day and discarded. Cleaning solutions are not typically utilized with these lenses. Frequent replacement contact lenses include lenses that may be reused for two weeks up to one month depending on the manufacturer's and/or the doctor's recommendation and generally require cleaning and disinfection every day. There are even contact lenses that are approved for longer periods of reuse. Frequent replacement lenses also include extended wear contact lenses which may be kept on eye for up to a week. Traditional contact lenses or reusable contact lenses are worn for much longer periods and are typically discarded approximately every six months.
Contact lens manufacturers as well as eye doctors recommend a certain replacement time (excluding daily disposable) for the different types of contact lenses for a number of reasons. For example, regardless of how well the contact lenses are cleaned and cared for, over time all contact lenses will get a buildup of protein, calcium and lipid deposits. These deposits may make the contact lenses less comfortable to wear and potentially make the eyes more prone to infection and irritation. Therefore, individuals need to keep track of the time the lenses are worn in order to be in compliance with recommendations.
Currently, there are no contact lenses with visible indicators to provide a patient, or in the case of pediatric use, to provide a parent with a clear signal that a contact lens has been used past its approved or recommended wear schedule. Accordingly, there exists a need for safety, health and/or other reasons, to develop a technology that would prevent wearing contact lenses beyond time periods designated for their replacement.